It is known to use magnetite, a naturally occurring iron oxide of the formula Fe3O4, in rubber compounds (Kautschuk Gummi Kunststoffe 56 (2003), pages 322 to 329). It is possible in this way to vary the heating capacity and the magnetic properties of the rubber compound. The average size (d50) of the magnetite particles used is in a range of approx. 10 to 60 μm. While it is true that their use enables the microwave heating capacity of the rubber compound to be increased, however, very high concentrations of magnetite are needed to achieve these effects. Even with these high concentrations, only a low heating rate results. Finally, the high concentration of magnetite leads to a disadvantageous change in the mechanical properties of the rubber compound.
From DE-A-10163399 a preparation is known in which superparamagnetic particles, containing at least one mixed metals oxide of the general formula M(II)M(III) O4, are present in dispersed form in a coherent phase. As the coherent phase, polymerisable monomers suitable for adhesives can be used. DE-A-10163399 gives no indications of the use of vulcanisable polymers.
A disadvantage of the particles used is their reagglomeration tendency during the production of the preparation. This can result in these particles losing their superparamagnetic properties. Moreover, there is the risk of uneven distribution of the particles in the preparation. To avoid this, the particles in DE-A-10163399 are preferably used in surface-modified form.